Learn Hardcore Italian: Il dipinto raffigura un fiore giallo.

Raffigura is the third-person singular present tense of raffigurare, which means “to depict” or “to portray.” It’s a transitive verb, so it directly takes an object. For example:
Il dipinto raffigura un fiore giallo.
(The painting depicts a yellow flower.)

Why is there no preposition between raffigura and un fiore giallo?

In Italian, transitive verbs like raffigurare can directly take a direct object without any preposition. The structure is simply:
subject + verb + direct object
You don’t need “to” or “of” as in English.

Why is the noun dipinto masculine and why is il used?

Dipinto (“painting”) is a masculine noun in Italian. All masculine singular nouns use the article il. There is no feminine counterpart here; the word dipinto itself is fixed as masculine.

Why do we say un fiore instead of il fiore or una fiore?

fiore is masculine, so the correct indefinite article is un (not una).
We use un because we’re introducing “a flower” in a general sense, not a specific flower already known to the listener.